Aims:1) To assess the role of lifetime residential exposure to radon and risk of lung cancer while taking into account active and passive exposure to cigarette smoke. 2) To contribute to national estimates of risk associated with radon exposure by pooling data with other studies of residential radon exposure and contrasting observed risk estimates with those predicted based on studies of uranium miners. 2) To explore other risk factors for lung cancer, including environmental exposures ascertained through linkage with geographically based data systems. Factors of interest include particulate matter air pollution, arsenic in drinking water, altitude, and numerous occupational, medical, and lifestyle factors ascertained from personal interviews. 3) To explore the risk for childhood cancers associated with residential radon exposure. Accomplishments: Data analysis has now been completed to assess lung cancer and childhood leukemia risk associated with residential radon exposure. For the lung cancer study, a uniform data structure has been created, allowing us to link a complex, multi-level data set. Residence addresses have been geocoded to facilitate linkage with geographical databases on factors associated with radon levels in homes. Housing characteristics associated with radon levels have also been identified and methods for dealing with missing exposure data have been evaluated. Although radon levels are lower than predicted, our coverage of the exposure time-window of interest is quite good. 20% of study subjects have complete coverage of the years between age 25 and 5-years before diagnosis. 60% have complete data for the years between 25 and 5 years prior to diagnosis or interview. Results suggest little overall lung cancer risk from radon at the low doses studied, but the data are consistent with estimates based on extrapolating from known effects in miners. Data on particulate matter air pollution have been obtained and a mapping strategy has been devised to estimate exposures for all houses in the study sample. Maps have been completed and analysis has begun to evaluate the link between this exposure and lung cancer risk. A similar approach will be used to link residences to information on arsenic in drinking water. Additional analyses will focus on high risk subtypes and other lung cancer risk factors such as environmental tobacco smoke exposure, occupational factors, altitude, and prior lung disease.